We had had the previous version of Mapp Enterprise running for sometime, recently we decided to upgrade to 16.1 Sp2.
During the installation of Mapp Enterprise 16.1 SP2, you will see a Mail Server setup session asking you to configure the SMTP server. It retains the previous information.
We ticked the Enable SSL box and then clicked the Test button to test the setup. An error message came up. To workaround that, we closed the error window and then toggled the Enable SSL settings a couple of times (i.e., tick and untick and tick) before we can get it working properly.
Highly recommend to use the Test button to test if the mail server has been set up properly, if not, you will not be able to create new users in Mapp Enterprise (could cause other implications too).